A single crystal diamond having high hardness and high strength, and further being excellent in thermal conductivity is industrially used in a wide range of applications including in addition to a wear-resistant tool such as a tool for grindstone dresser, a die for wire drawing, a scribe tool, an orifice for water jet, and a wire guide, a diamond tool for cutting, and the like.
As a single crystal diamond used for a diamond product, a natural diamond and a synthetic diamond can be mentioned. Most of naturally occurring diamond single crystals belong to an Ia type, and contain around several hundreds to several thousands of ppm of nitrogen in a form of aggregating in a plate shape between lattices. In an Ia-type diamond single crystal, the content of impurities, the density and generation form of plate-like defects are varied even within the same crystal, and further the variation due to individual differences among crystals is large, therefore, the quality and performance are not stable. Moreover, among natural diamond single crystals, a high-purity product having less than or equal to several ppm of nitrogen impurities is called type IIa. The IIa-type diamond single crystal has extremely few impurities, but has many internal distortion and defects, therefore is not suitable for tool applications.
On the other hand, in synthetic diamonds, a synthetic diamond having a constant quality can be stably supplied. Therefore, synthetic diamonds are widely used in an industrial field.